So the question of whether TLD MXs work depends on the interactions
between lot of complicated option settings and software versions, and is
likely in practice to work or fail unpredictably.
That sounds utterly reasonable.
To me the bigger question is whether this failure scenario is something
the IETF needs to address, or is it is sufficiently localized that it's
something that just another thing a domain owner should deal with.
Personally, I don't think that foo@ai -> foo@xxxxxxxxxx is a major issue,
because in recent years mail addressing has gotten rather flat, most DNS
resolvers are configured via DHCP, and I don't get the impression that
they have any search lists at all. Search lists were useful 15 or 20
years ago, but not now. It would be interesting to hear from people
running mail systems who were NOT running them ten years ago, to avoid the
selection bias of people whose configuration preferences were set on the
T1 backbone.
Regards,
John Levine, johnl@xxxxxxxx, Primary Perpetrator of "The Internet for Dummies",
Information Superhighwayman wanna-be, http://www.johnlevine.com, ex-Mayor
"More Wiener schnitzel, please", said Tom, revealingly.
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